that i dont know for sure, but what would be the difference between factory oe valves and FR valves? the material the valves are made from wouldnt make any difference between OE and a high performance material unless you are making an extreme level of power that pushes temps that would melt the OE valves. the valves in the FR head are the same exact size as OE. to the best of my knowledge the FR head is just a bone stock head with a P&P and valve job everything else OE. and i THINK it might have been clearanced for big cams too but i might be mistaken on that. if you want to know for 100% sure i suggest calling massive and asking them. they probably sold more FR heads than any other aftermarket focus parts seller and are just really helpful in general.